WASHINGTON — The Pentagon has lifted some flight restrictions on F-35 Joint Strike Fighters, while inspections will continue for the foreseeable future, according to a Defense Department official.

Article updated July 30, 2014.

Speed restrictions for the 20 F-35s that make up the test aircraft fleet were relaxed late last week from Mach 0.9 to Mach 1.6, while maneuverability restrictions were increased slightly from 3 Gs to 3.2, the official said.

Other restrictions remain, however, including borescope inspections of the front fan section of each F135 engine every three hours. The 79 remaining F-35s are still under the full restrictions.

The restrictions are the result of a June 23 fire that severely damaged an F-35A model and led to the Pentagon grounding the fleet for a time while the cause of the problem was discovered. On July 15, the Pentagon allowed the plane to begin flying again within limited parameters.

Those restrictions are limiting the ability of the services to fully test and evaluate the planes, meaning that if the restrictions remain for a significant period, it could affect the planned initial operating capability (IOC) dates for the jet.

The Marine Corps’ aircraft will be the first to reach IOC — in July 2015 — followed by the Air Force in August 2016.

Asked whether there is a date on the calendar when the restrictions would begin to threaten Marine IOC, the official said he “can’t put a timeline on that,” noting the restrictions will continue to loosen as engineering assessments warrant.

A top general for the US Air Force expressed confidence that his service, the largest customer for the jet, remains on target for IOC — at least for now.

“So far the schedule impacts are relatively minimal,” Gen. Michael Hostage, the head of Air Combat Command, told reporters on Tuesday. “I still believe we can get to IOC in August of 2016 for the Air Force. But every day makes that a little harder to do.”

Hostage said it would be more a matter of weeks, not months, that the jet would operate under restrictions.

“I don’t think it’s going to be much longer,” he said. “We’re narrowing it down pretty quickly. But you want certainty. If it’s going to be an expensive fix you don’t want to spend a lot of money to figure out that wasn’t it, so you want to have certainty before you commit yourself to anything.”

Hostage praised the fusion capabilities of the F-35 as game-changing when compared to legacy fighters, and defended the plane despite questions about its overall cost.

“I am confident that if we can produce the 1,763 F-35s at the cost the industry and the JPO [Joint Program Office] are forecasting, we’ll have a fleet that will defend this country as far into the 2030s as we expect it to,” Hostage said.